(a) Field of the Invention
The present invention relates to a handover method, and particularly it relates to a handover method using a MAC (Media Access Control) address of less than 64 bits in a mobile IPv6 (Internet Protocol version 6) to automatically reserve addresses for a handover.
(b) Description of the Related Art
As the use of Internet has been explosively increased, the internet protocol IP (Internet Protocol) has lead technology on existing data networks and wired/wireless communication networks. Accordingly, standardization in networks has been accelerated under an AII-IP architecture forming an IP-based network: from a terminal to a core network.
A Mobile IPv6 developed by IETF (Internet Engineering Task Force) is the most leading technology that supports mobility to each node in the next-generation Internet Protocol, IP version 6 (IPv6). Similar to mobile IPv4, the mobile IPv6 [D. Johnson et. Al, mobility Support in IPv6, draft-ietf-mobileip-ipv6-24.txt, 2003, 6] is designed to provide transparent mobility to upper layers including a transport control protocol (TCP) layer from a network layer. A mobile host in the mobile IPv6 sends a binding update to a home agent (HA) and associated corresponding nodes (CNs) using a care-of-address (CoA) to update a current location to maintain connectivity to the Internet when the mobile host changes its access router for another.
FIG. 1 illustrates a handover in a conventional mobile IPv6.
In the conventional mobile IPv6 network, as shown in FIG. 1, a Layer 2 handover occurs, in Step of S101. The Layer 2 handover represents a physical change of a link. Then, a Layer 3 handover is detected through neighbor unreachability detection in the Layer 3, in Step of S102. Once the Layer 3 handover is detected, a mobile node creates a new link-local address valid in a current link, in Step of S103. Herein, the new link-local address may be occupied by other nodes, and therefore the mobile node needs to verify the uniqueness of the new link-local address by performing a Duplicated Address Detection (DAD) process, in Step of S104. Once the new link-local address is verified, the mobile node discovers its default router in consequence to a Router Discovery process in Step of S105, and discovers prefix information attached to the default router in Step of S106. Further, the mobile node creates a global address for its own use based on the prefix information in Step of S107. Herein, the new global address also must be verified through the DAD process in Step of S108. Once the new global address is verified, the mobile node registers the new global address with the HA in Step of S109 and sends the binding update to the associated CNs using the new global address in Step of S110.
As described, the mobile node in the conventional mobile IPv6 performs the DAD process twice for the new link-local address and the new global address, and each DAD process consumes at least one second. Further, the mobile node detects its movement in the Layer 3 by receiving a Router Advertisement message. The Router Advertisement message is delivered on every three seconds in accordance with the IPv6 standard. A delivery interval of the Router Advertisement message is set to be 30 ms to 70 ms in the mobile IPv6, but it is difficult to be substantially implemented by a router.
Further, similar to the mobile IPv4, the mobile IPv6 is designed to support mobility in a wide area, and thus handover latency during a registration process may be an obstacle for to support a real-time service including a VoIP (Voice Over IP) which will be an essential part of the Internet in the near future. Hence, the IETF group studies various methods to support a fast handover in the mobile IPv6 so as to overcome the handover latency.
HMIPv6 [Hesham Soliman, Hierarchical MIPv6 mobility management, IETF Internet Draft draft-ieff-mobileip-hmipv6-07.txt, 2002. 10] is one of disclosed methods to support the fast handover. The mobile node in the conventional mobile IP is required to register its new CoA with an HA which may be located away whenever the mobile node moves, and thereby inducing unacceptable handover latency. However, the mobile node in the HMIPv6 registers the new CoA with a MAP (Mobile Anchor Point) whenever the mobile node moves to another subnets and thereby minimizing the handover latency since it takes less time to bind-update a local MAP than a distant HA. However, the time for the binding update of the Layer 3 is partially reduced because the binding update of the Layer 3 is performed after completion of the binding update of the Layer 2.
FMIPv6 [G. Dommety, Fast Handovers for Mobile IPv6, IETF Internet Draft draft-ieff-mobileip-fast-mipv6-60.txt, 2003. 3] is another method to support the fast handover. The FMIPv6 is designed to reduce handover latency at Layer 3 using handover trigger information sent from Layer 2 so as to offer the real-time service including the VoIP of the mobile nodes in the IP network. In the FMIPv6, the mobile node receives a trigger message pre-notifying occurrence of Layer 2 handover, and begins to a process of new CoA (NCoA) assignment while the mobile node is still attached to a current access router. Further, a bi-directional tunnel is established between the current access router (previous access router, PAR) and a new access router (NAR) to prevent loss of data until completion of the binding updates to the NCoA.
Such a fast handover method may reduce the handover latency by creating a NCoA which may increase the handover latency and performing the DAD process to verify the NCoA prior to the occurrence of the handover, but the process of the fast handover method can be complicated and the handover latency can be more increased if the Layer 2 trigger message is not timely sent.
Further, although the foregoing handover methods support the handover in the mobile IPv6, IPv6 stateless address auto-configuration restricts to support the handover. In other words, the foregoing handover methods require an additional process including the DAD process to verify an automatically generated new address, and the DAD process consumes at least one second under an optimal condition and thereby adds delay to the handover (in the case of the mobile HMIPv6) and causes a more complicated and unstable handover process (in the case of the fast handover method).
Accordingly, simplification of movement detection and the DAD process of the mobile IPv6 may reduce the handover latency and thereby support real-time applications. Further, the handover performance will be more enhanced when the simplified handover is combined to the HMIPv6 that is the most efficient method of reducing the binding update time.